Most likely a mythical modern retelling of a mystic group of hallucinogenic mushroom-eating Siberian shaman who wore red and white outfits, snuck in through the chimneys of villagers and distributed the sacred mushroom Amanita Muscaria. Other associations from the popular myth easily fall into place. The reindeer is the animal most associated with Amanita as it is a popular dish to them. Amanita tends to form a symbotic relationship with spruce or pine trees which are used for Christmas trees. It is also said that the Siberian shaman could fly, but probably not physically. However, Amanita often gives the sensation of flying.
Santa Claus was just a crazy mushroom cult all along.